Yaxcopoil-1 and the Chicxulub impact     

Wolfgang?StinnesbeckEmail author  Gerta?Keller  Thierry?Adatte  Markus?Harting  Doris?Stüben  Georg?Istrate  Utz?Kramar 《International Journal of Earth Sciences》2004,93(6):1042-1065

CSDP core Yaxcopoil-1 was drilled to a depth of 1,511 m within the Chicxulub crater. An organic-rich marly limestone near the base of the hole (1,495 to 1,452 m) was deposited in an open marine shelf environment during the latest Cenomanian (uppermost Rotalipora cushmani zone). The overlying sequence of limestones, dolomites and anhydrites (1,495 to 894 m) indicates deposition in various carbonate platform environments (e.g., sabkhas, lagoons). A 100-m-thick suevite breccia (894–794 m) identifies the Chicxulub impact event. Above the suevite breccia is a dolomitic limestone with planktic foraminiferal assemblages indicative of Plummerita hantkeninoides zone CF1, which spans the last 300 ky of the Maastrichtian. An erosional surface 50 cm above the breccia/dolomite contact marks the K/T boundary and a hiatus. Limestones above this contact contain the first Tertiary planktic foraminifera indicative of an upper P. eugubina zone P1a(2) age. Another hiatus 7 cm upsection separates zone P1a(2) and hemipelagic limestones of planktic foraminiferal Zone P1c. Planktic foraminiferal assemblages of Zone Plc to P3b age are present from a depth of 794.04 up to 775 m. The Cretaceous carbonate sequence appears to be autochthonous, with a stratigraphic sequence comparable to late Cretaceous sediments known from outside the Chicxulub crater in northern and southern Yucatan, including the late Cenomanian organic-rich marly limestone. There is no evidence that these sediments represent crater infill due to megablocks sliding into the crater, such as major disruption of sediments, chaotic changes in lithology, overturned or deep dipping megablocks, major mechanical fragmentation, shock or thermal alteration, or ductile deformation. Breccia units that are intercalated in the carbonate platform sequence are intraformational in origin (e.g., dissolution of evaporites) and dykes are rare. Major disturbances of strata by the impact therefore appear to have been confined to within less than 60 km from the proposed impact center. Yaxcopoil-1 may be located outside the collapsed transient crater cavity, either on the upper end of an elevated and tilted horst of the terrace zone, or even outside the annular crater cavity. The Chicxulub site thus records a large impact that predates the K/T boundary impact and mass extinction.  相似文献   

Palaeogeography and tectonic structure of allochthonous units in the German part of the Rheno-Hercynian Belt (Central European Variscides)     

H.?HuckriedeEmail author  K.?Wemmer  H.?Ahrendt 《International Journal of Earth Sciences》2004,93(3):414-431

New information on palaeogeography, orogenic evolution, tectonic structure, and boundaries of allochthonous units in the Rheno-Hercynian Belt is based on provenance analyses of clastic sediments and field studies. ⁴⁰K/⁴⁰Ar dating of detrital muscovites proved to be a particularly useful method because Cadomian, Caledonian and Early Variscan provenances of detrital material can be distinguished. Cadomian muscovite cooling ages are restricted to allochthonous units whereas Caledonian ages dominate within par-autochthonous and shortly displaced allochthonous units. The largest and uppermost preserved nappe, the Gießen-Harz Nappe, is derived from an oceanic flysch basin, which was not reached by Caledonian detritus. The other allochthonous units form a duplex-like structure sandwiched between the Gießen-Harz Nappe and par-autochthonous units at its base. The thick and heterogeneous roof- and floor-thrusts of this structure were previously often misinterpreted as olistostromes. The northern margin of allochthonous units is the steeply dipping Hörre-Gommern Zone. It consists of three sub-units derived from deep-water areas between the shelf at the southern margin of the Old Red Sandstone Continent and an oceanic basin to the south. The southeastern part of the duplex-structure (Harzgerode Zone) shows close affinities to Armorican terranes.  相似文献   

南极地区Es特性研究          下载免费PDF全文

赵海生  许正文  吴健 《极地研究》2012,24(2):129-135

Es是发生在电离层E层高度上的偶发电离增强结构,其电子密度最高可达E层背景电子密度的100倍以上。Es出现概率和强度全球分布不均,主要分布在中低纬度地区,极区也有较强Es出现并具有显著特点,极区Es的研究,对研究Es成因和物理机理具有重要科学意义。本文利用Syowa站（69.0°S,39.6°E）40余年的观测数据,选取临界频率和虚高两个参数,研究了南极地区Es强度特性、日变化、季节变化及长期变化特性。  相似文献   

酸雨观测异常数据的试验分析和处理方法     

茆越  孙明  施勇  茆金祥 《气象科学》2012,32(S1):46-50

本文就酸雨观测仪器在测量操作中出现的异常状态进行了试验和分析,且对校错电极常数、测温系统故障、"后测K值"3种异常状态, 结合酸雨观测业务实践进行了试验、分析和讨论。推导出校错电极常数的电导率订正公式;制定了仪器测温系统故障的应急观测方案;指出"后测K值"会导致数据严重失真, 测量中必须严格遵循 "先测K值"规程;并建议在《酸雨观测业务规范》修订时, 增加本文有关的分析和处理方法。  相似文献   

K干旱指数在甘肃省干旱监测业务中的应用   总被引：4，自引：0，他引：4  

王劲松  任余龙  宋秀玲 《干旱气象》2008,26(4):75-79

利用K干旱指数及其干旱监测预测业务系统,着重介绍了K干旱指数在甘肃省干旱监测业务中的应用。从K干旱指数的定义、等级、标准、应用及其监测结果与实际干旱状况的比较方面进行了分析。结果表明,与实际的旱情比较,K干旱指数在甘肃省2008年春季、5月、6月、伏期（7—8月）以及秋季前期9月的干旱监测中有较好的监测效果。  相似文献   

Chromium speciation in oxide-type compounds: application to minerals,gems, aqueous solutions and silicate glasses     

François Farges 《Physics and Chemistry of Minerals》2009,36(8):463-481

Cr K-edge XANES spectra were obtained for a variety of Cr-bearing model compounds containing Cr(II), Cr(III), Cr(IV), Cr(V) and Cr(VI), in which the Cr-site symmetry is D4h, Oh and Td. The centroid position of the pre-edge feature is a better indicator of the Cr valence than the edge position. In Cr-rich oxides, higher-energy transitions must be excluded in order to refine a robust valence for Cr. The pre-edge for chromates is not unique and varies as a function of the CrO₄ ^2? moiety distortion, which is often related to Cr-polymerization (monochromate vs. dichromate). Both the analogy with the Mn K-pre-edge information and ab initio FEFF calculations of the pre-edge feature for Cr(III) and Cr(VI) confirm the experimental trends. This methodology is applied to the Cr K-edge pre-edge feature collected in gems (emerald, spinel and ruby), the layered minerals fuchsite and kämmererite, two Cr-bearing aqueous solutions and a set of sodo-calcic silicate glasses used for bottling sparkling white wine. In emerald and fuchsite, the Cr-site is differently distorted than its ruby or spinel counterpart. In a Cr(III)-bearing aqueous solution and sodo-calcic glass, no evidence for Cr(III) with Td and C3v symmetry is detected. However, minor amounts of chromate moieties (most likely monomeric) are detected in a glass synthesized in air. Preliminary spectra for the wine bottle glass suggest that only trace amounts of chromates might possibly be present in these glasses.  相似文献   

Is Comet C/1853 E1 (Secchi) extrasolar?     

R.L. Branham 《Astronomische Nachrichten》2012,333(2):118-124

Comet C/1853 E1 (Secchi) has a hyperbolic orbit with eccentricity 1.01060 and perihelion outside of the Earth's orbit. Integrating the orbit with barycentric coordinates backwards to 50000 AU, the approximate edge of the Oort cloud, shows that the orbit remains hyperbolic. This is still true even if plutoids additional to Pluto are included in the integration. Nor does including Galactic tidal and disc effects and possible nongravitational forces change the orbit to a high eccentricity ellipse. Although certain factors, such as unknown massive plutoids, gravitational effects by interstellar gas clouds, or unmodelled nongravitational forces operating on the comet, could change this situation, the tentative conclusion that the origin of this comet is extrasolar remains the one most consistent with the observations (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

固定铝log(Q/K)图解在温泉中的应用     

张展适  孙占学  李满根  王素娟 《地球科学》2004,29(3):352-356

为探讨常规和固定铝log(Q/K)图解法对温泉系统是否有效 ,采用WATCH程序 ,对江西 3个温度较高的温泉 ,即庐山温泉、汤湖温泉和横泾温泉 ,进行了探测性的研究 .采用常规log(Q/K)图解法计算时 ,由于参加计算的 4个水样的铝含量均未检出 ,计算结果显示只有不含铝的矿物玉髓和方解石相交于温度 1 0 0℃附近 ,热储总体上没有达到平衡 .在采用了固定铝log(Q/K)图解法并同时考虑冷水的稀释作用计算后 ,中低温地热系统中常见的蚀变矿物如浊沸石、纤蛇纹石、萤石和玉髓均显示了较好的收敛性 ,收敛的温度大致在 1 0 0～ 1 4 0℃ .并且上述矿物组合可见于某些温泉的深部钻孔中 ,计算结果与实际地质情况相吻合 .结果表明固定铝log(Q/K)图解法可以恢复温泉系统的热平衡状态  相似文献   

Ordovician Granitoids and Silurian Mafic Dikes in the Western Kunlun Orogen, Northwest China: Implications for Evolution of the Proto-Tethys     

ZHANG Qichao  WU Zhenhan  LI Shan  LI Kan  LIU Zhiwei  ZHOU Qing 《《地质学报》英文版》2019,93(1):30-49

The western Kunlun orogen in the northwest Tibet Plateau is related to subduction and collision of Proto-and Paleo-Tethys from early Paleozoic to early Mesozoic. This paper presents new LA-ICPMS zircon U-Pb ages and Lu-Hf isotopes, whole-rock major and trace elements, and Sr–Nd isotopes of two Ordovician granitoid plutons(466–455 Ma) and their Silurian mafic dikes(～436 Ma) in the western Kunlun orogen. These granitoids show peraluminous high-K calcalkaline characteristics, with(⁸⁷Sr/⁸⁶Sr)_i value of 0.7129–0.7224, ε_Nd(t) values of -9.3 to -7.0 and zircon ε_Hf(t) values of -17.3 to -0.2, indicating that they were formed by partial melting of ancient lower-crust(metaigneous rocks mixed with metasedimentary rocks) with some mantle materials in response to subduction of the Proto-Tethyan Ocean and following collision. The Silurian mafic dikes were considered to have been derived from a low degree of partial melting of primary mafic magma. These mafic dikes show initial ⁸⁷Sr/⁸⁶Sr ratios of 0.7101–0.7152 and ε_Nd(t) values of -3.8 to -3.4 and zircon ε_Hf(t) values of -8.8 to -4.9, indicating that they were derived from enriched mantle in response to post-collisional slab break-off. Combined with regional geology, our new data provide valuable insight into late evolution of the Proto-Tethys.  相似文献   

覆盆子-红花药对与男性不育症的治疗相关机制探讨          下载免费PDF全文

曾小艳  童丽 《应用海洋学学报》2021,37(1):147

目的：基于网络药理学探讨覆盆子-红花药对治疗男性不育症的物质基础及作用机制。方法：用TCMSP数据库检索覆盆子、红花,收集其化学成分以及靶点信息;用GeneCards和OMIM数据库筛选男性不育症的疾病靶点;应用韦恩图筛选药物与疾病的共同靶点;应用R软件进行GO富集分析及KEGG分析;应用 Cytoscape 3.7.2 软件构建药物-活性成分-疾病-靶点互作网络。结果：从覆盆子、红花得到了22个活性成分及202个药物靶点。在药物-活性成分-疾病-靶点互作网络中,degree值较高的为槲皮素及木犀草素,表明覆盆子-红花药对治疗男性不育症的主要活性成分可能为槲皮素、木犀草素等。覆盆子-红花药对治疗男性不育症的可能靶点有131个,其中核心靶点为ALB、AKT1、IL-6、VEGFA、JUN等,这些靶点主要与氧化及抗氧化生物等生物学过程相关。覆盆子-红花药对的靶点主要通过P13K/Akt信号通道治疗男性不育症。结论：覆盆子-红花药对通过多靶点、多途径治疗男性不育症。本研究为开展覆盆子-红花药对治疗男性不育症的实验提供了理论基础,为男性不育症的治疗提供了更多的思路。  相似文献